title: Network structures of Bis-GMA/TEGDMA resins differ in DC, shrinkage-strain, hardness and optical properties as a function of reducing agent.
abstract: OBJECTIVE
  To evaluate the influence of different tertiary amines on degree of conversion (DC), shrinkage-strain, shrinkage-strain rate, Knoop microhardness, and color and transmittance stabilities of experimental resins containing BisGMA/TEGDMA (3:1wt), 0.25wt% camphorquinone, 1wt% amine (DMAEMA, CEMA, DMPT, DEPT or DABE). Different light-curing protocols were also evaluated.
  
  
  METHODS
  DC was evaluated with FTIR-ATR and shrinkage-strain with the bonded-disk method. Shrinkage-strain-rate data were obtained from numerical differentiation of shrinkage-strain data with respect to time. Color stability and transmittance were evaluated after different periods of artificial aging, according to ISO 7491:2000. Results were evaluated with ANOVA, Tukey, and Dunnett's T3 tests (α=0.05).
  
  
  RESULTS
  Studied properties were influenced by amines. DC and shrinkage-strain were maximum at the sequence: CQ<DEPT<DMPT≤CEMA≈DABE<DMAEMA. Both DC and shrinkage were also influenced by the curing protocol, with positive correlations between DC and shrinkage-strain and DC and shrinkage-strain rate. Materials generally decreased in L* and increased in b*. The strong exception was the resin containing DMAEMA that did not show dark and yellow shifts. Color varied in the sequence: DMAEMA<DEPT<DMPT<CEMA<DABE. Transmittance varied in the sequence: DEPT≈DABE<DABE≈DMPT≈CEMA<DMPT≈CEMA≈DMAEMA, being more evident at the wavelength of 400nm. No correlations between DC and optical properties were observed.
  
  
  CONCLUSIONS
  The resin containing DMAEMA showed higher DC, shrinkage-strain, shrinkage-strain rate, and microhardness, in addition to better optical properties.
authors.affiliation: Master of Science Program in Clinical Dentistry, Department of Dentistry, Positivo University, Rua Professor Pedro Viriato Parigot de Souza, 5300, CEP 81280-330 Curitiba, PR, Brazil. furuseay@yahoo.com.br
authors.forename: Adilson Y
authors.initials: AY
authors.lastname: Furuse
authors.forename: José
authors.initials: J
authors.lastname: Mondelli
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry; D000814:Aniline Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D008027:Light; D008689:Methacrylates / Q000737:chemistry; D058567:Photoinitiators, Dental / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry*; D019163:Reducing Agents / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D014052:Toluidines / Q000737:chemistry; D062366:para-Aminobenzoates
chemical_list: D000814:Aniline Compounds; D003188:Composite Resins; D008689:Methacrylates; D058567:Photoinitiators, Dental; D011109:Polymethacrylic Acids; D019163:Reducing Agents; D013729:Terpenes; D014052:Toluidines; D062366:para-Aminobenzoates; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; C076186:3-(N-methylanilino)propiononitrile; C030746:4-(dimethylamino)benzoic acid; C049840:2-(dimethylamino)ethyl methacrylate; C015835:dimethyl-4-toluidine; D010129:4-Aminobenzoic Acid